Starting this July, the first iPhone developers from last year will start having their iPhone Developer Program memberships expire. A developer cannot submit updates after the membership has expired, but presumably the app would be removed from the App Store as well. (I’m not sure if anyone actually knows whether that’s the case.)
This is actually a good mechanism: it’s an automatic removal of abandoned apps. It will probably help remove a lot of the gold-rush crapware, but a few legitimately good apps might disappear as well if the developer either forgot to renew the membership or no longer felt that it was worthwhile. Users of removed apps can continue using them, but they can never gain any new users, effectively forcing the apps’ death.
I wonder how many apps will disappear before September.